Greetings!
It's been one of those days. I'm sure it's because I stayed up too late. Regardless, I was able to get a few things done. After carrying the heavy rear axle into the shop yesterday, I spent some time taking it apart so I could get it cleaned up. There are casting marks that the GM factory puts on these axles so you can know where and when it was made. Supposedly, it also has a code for the gear ratio - a very important hot rod ingredient.
I found the casting marks in the axle tubing and tried to determine which numbers referred to the gear ratio, but didn't find the markings listed in any of my resources. So, I thought I'd do it the easy way and I put marked tape on the axle and pinion so I could count the number of rotations. That would give me at least an approximate idea of the gear ratio.
The pinion (shaped like an archway in the photo) rotated about 2.4 times per revolution of the axle. That's pretty high gearing if my little test is accurate. I checked online and there was an axle gear ratio of 2.41:1 made in '78 Camaros, and that's what year this one came from. With the 4-speed that Gary has selected the rear axle ratio would allow him to cruise on the freeway at a low RPM, but he'd just about need a push start to get his car rolling from a dead stop.
The pinion (shaped like an archway in the photo) rotated about 2.4 times per revolution of the axle. That's pretty high gearing if my little test is accurate. I checked online and there was an axle gear ratio of 2.41:1 made in '78 Camaros, and that's what year this one came from. With the 4-speed that Gary has selected the rear axle ratio would allow him to cruise on the freeway at a low RPM, but he'd just about need a push start to get his car rolling from a dead stop.
The car isn't particularly heavy at just over 3,000lbs, so if I get his axle gearing to a lower ratio (but higher number) like 3.08:1, it would make the '51 a blast to drive around town and still allow him to get the thumbs up from admirers on the freeway.
As you can see by the shiny marks on the axle, I ground off the previous spring perches. The perches are what hold the axle to the leaf springs and they were too wide to fit the springs under the little coupe. Thinking I was very clever, I set the axle up on jackstands, unbolted the rear cover and let the old oil drain out into a pan. Neat and tidy. Just the way I like things.
As it was draining I thought I'd make good use of my time and remove the brake backing plates so I could bead blast them prior to painting. I had to resort to my high torque, 1/2" drive air ratchet to break them loose and the torque of the ratchet on the super-tight bolts spun the differential around and it fell from it's perch into the bucket of old oil. Dang.
I managed to get things cleaned up (the maid had the day off) and took the bad-boy backing plates to the bead blasting box for a bit. I'm going to use POR-15 to paint the backing plates and the axle. It's a paint product that can be applied over a surface that isn't totally free of rust. It apparently neutralizes the rust and stays on forever. Tip: you don't want to spill POR-15 on anything you can't enjoy in black. By the way, I think they're making the stuff in other colors besides black now.
Quick Question: If you knew a beautiful woman who was constantly contradicting herself, would you call her a foxymoron?
Monday, I'll take the axle to Highway Auto Wrecking in Grandview (509 882-1770) to have the new 3.08 gear set installed. It's not something that my humble little shop is set up to do. It requires special tools and plenty of experience with rear ends. While the axle is tied up in the shop I plan to take the 'yard art' 305 V8 apart and have it machined and prepped for re-assembly by my buddy, Brian, at K&U Auto Parts (509 837-5603) in Sunnyside. He's an excellent machinist and my engine blocks always come back spotlessly clean inside and out. It'll be a busy week coming up. And, I hear that we have some snow coming...
Doug
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